A water area structure using a placing member for underwater ground is well known in the art, and is constructed as shown in FIGS. 82 and 83. In the conventional water area structure, a number of steel sheet piles 48 engaged with each other are driven into underwater ground 2 to form a sheet pile wall 49. A number of piles 5 are disposed at a position spaced from the sheet pile wall 49 at regular intervals in the longitudinal direction of the sheet pile wall, and are driven into the underwater ground 2. A number of diagonal piles 50 diagonally downwardly extend from an upper portion of the sheet pile wall 49 toward the underwater ground 2 in a vertical plane substantially perpendicular to the sheet pile wall 49. The diagonal piles 50 are disposed at intervals in the longitudinal direction of the sheet pile wall, and are driven into the underwater ground 2. The upper end of the sheet pile wall 49, that of the diagonal pile 50, and that of the pile 5 are coupled through a coupling member 6 comprising a concrete slab. Back-fill earth 51 and earth filling 52 are filled at the back of the sheet pile wall 49.
In the water area structure using the conventional placing member for underwater ground, axial supporting force of the ground, i.e., the distal supporting force of the pile and circumferential frictional force of the pile give resistance to forcing pressure generated in the diagonal pile 50. The forcing pressure, however, is excessively high. Therefore, generally, it is necessary to considerably extend a length of the diagonal pile 50 which is driven into hard bearing stratum 53 to obtain the sufficient supporting force of the pile end.
On the other hand, axial supporting force of the ground (circumferential frictional force) gives resistance to drawing force generated in the sheet pile wall 49. The drawing force, however, is also excessively high. Thus, generally, it is necessary to considerably extend a length of the sheet pile wall 49 which is driven into the hard bearing stratum 53 to obtain the sufficient circumferential frictional force.
As set forth above, in the water area structure using the conventional placing member for underwater ground, it is essential to drive the diagonal pile 50 and the sheet pile wall 49 into the hard bearing stratum 53 by each considerable length to support each excessively high axial force generated in the diagonal pile 50 and the sheet pile wall 49. As a result, there were some drawbacks such as long time required for execution, or buckling of the diagonal pile 50 and the steel sheet pile 48 as well as very costly materials.
In execution of driving the diagonal pile 50, a canted angle of the diagonal pile 50 with respect to a vertical line ((typically, in the range of 10 to 20 degrees) can not be further increased. Therefore, it was too difficult to reduce the forcing pressure generated in the diagonal pile 50. Additionally, if the diagonal pile 50 is excessively long, it is too hard to drive it straightforwardly at a predetermined canted angle. The diagonal pile 50 may be deviated from the predetermined angle during driving. As a result, there was another drawback of occurrence of secondary stress due to bending, in addition to loss of a desired supporting force.
Pile 5 substantially gives no resistance to horizontal external force such as earth pressure, hydraulic pressure in the ground, or seismic force. Pile 5 supports only vertically downward load such as deadweight or live load of the upper concrete. In addition, banking may be provided in front of the sheet pile wall 49 to enhance stability of the water area structure. In this case, the diagonal pile 50 has excessively high bending moment generated by weight of the banking. As a result, considerably large sectional strength is required for the diagonal pile 50. Thus, there is another drawback of costly material and costly execution for the diagonal pile 50.
As described hereinbefore, in the water area structure using the conventional placing member for underwater ground, the diagonal pile 50 and the sheet pile wall 49 are arranged to have axial supporting force for giving main resistance to the horizontal external force such as the earth pressure, the hydraulic pressure in the ground, or seismic force. Therefore, the conventional structure can not take full advantage of transverse supporting force, which is one of several supporting force functions in the ground.
Thus, it is a first object of the present invention to provide a water area structure using a placing member for underwater ground, which enables to efficiently take advantage of supporting force functions in a ground, i.e., axial supporting force and transverse supporting force.
In the invention, compressive force applied to diagonal member is converted into forcing pressure, bending moment, and shearing force applied to a pile in a connecting portion between diagonal member and the pile. Accordingly, the forcing pressure generated in the pile can be considerably decreased to reduce a depth by which the pile is driven into the hard bearing stratum. Thereby, it is a second object of the invention to improve efficiency in execution of driving the pile, and to avoid local buckling of the pile.
Further, in the invention, the drawing force generated in the sheet pile wall can be also reduced as well as the forcing pressure generated in the forward pile. Consequently, it is possible to reduce a depth by which the sheet pile wall is driven into the hard bearing stratum. Thus, it is a third object of the invention to improve efficiency in execution of the sheet pile wall, and to avoid local buckling of the steel sheet pile.
It is a fourth object of the invention to provide a large canted angle of diagonal member with respect to a vertical line, and to further reduce the axial force generated in the forward pile or the sheet pile wall.
In the invention, the pile and the sheet pile wall driven into the underwater ground give resistance to external force such as earth pressure, hydraulic pressure in the ground, or seismic force. In this case, both the axial supporting force and the transverse supporting force generated in the underwater ground can be efficiently used. The canted angle of the diagonal member can be optionally determined with respect to a vertical line. Thus, it is a fifth object of the invention to adjust axial force generated in the pile or the sheet pile wall according to ground condition, condition of the external force, or the like, and to enhance degree of freedom in designation tremendously.
Further, it is a sixth object of the invention to reduce cost required for construction to a great extent by reducing amount of material used for a water area structure, and improving execution efficiency.
Moreover, it is a seventh object of the invention to arrange the piles and the diagonal members closely in front of the sheet pile wall, and to provide a fish school effect in that a flock of fish are easy to gather.